Generally, extrusion is the process by which a block or billet of metal is reduced in cross section and shaped by forcing it to flow through a die under high pressure. Most metals are hot extruded due to the large amount of forces required in extrusion. In a typical extrusion process, an extrusion billet is heated and placed in a container of a hydraulic extrusion press. A dummy block is placed between the ram of the extrusion press and the heated billet. The ram then applies pressure to the heated billet and forces the billet through a shaped die to form an extrusion product.
The physical properties of a metal may be advantageously influenced by the presence of one or more other metals. For example, the combination of two or more metals (i.e., alloying) may provide improved or changed thermal conductivity, electrical conductivity, or tensile properties in comparison to either of the pure metals. Accordingly, it is desirable to formulate metal materials containing more than one metal. This may be accomplished by casting, wherein each metal is melted to its molten form and then solidified together. This may also be accomplished by extrusion, wherein each metal is in its solid form. It has generally been considered, however, that hot extrusion in which a molten metal is contained within a solid metal carrier cannot be achieved due to the high extrusion forces and tendency for the molten metal to blow out of the solid metal carrier.